1) Field of the Invention
The present invention relates to a printer for printing information in a center-folding type book when the book is in the open state.
2) Description of the Related Art
Usually, this type of printer is incorporated into an automatic teller machine (ATM), a cash dispenser (CD) or the like installed in financial facilities, whereby transactions made therein are registered or printed out on the center-folding type book, such as a bankbook, passbook or the like, by the printer. These machine have an entrance port for inserting the book in the open state, and the inserted book is then guided to a printing position defined by a platen and a printing head of the printer. Information on the transaction, etc. is then printed out on the open pages of the book in parallel with the center-holding line thereof, while the book is moved step by step through the printing position, i.e., the gap between the platen and the printing head. In this case, one half side of the opened book may have a different thickness to that of the other half side thereof except where the book is opened at the center thereof so that both half sides thereof have the same thickness, and thus the gap between the platen and the printing head must be adjustable, to enable the printing to be always carried out at a constant optimum printing pressure on the half sides of the opened book each having a different thickness.
It has been proposed that the gap between the platen and the printing head be adjusted in response to a thickness of the half side of the opened book on which the information is to be printed, and therefore, in this printer, the platen is movable with respect to the printing head, and an adjustment of the gap therebetween is made by a movement of the platen whenever one half side of the opened book is newly positioned at the printing position. In particular, the platen is first moved toward the printing head until it is abutted against the half side of the opened book positioned therebetween, and is then moved back and away from the half side of the book by a given distance, so that a constant gap can be obtained between the printing head and the half side of the book regardless of a variation in the thickness thereof, whereby a constant optimum printing pressure can be ensured.
In the printer as mentioned above, the movement of the platen toward the printing head must be stopped when the platen abuts against the half side of the opened book, and accordingly, a movable rod-like element, which is associated with a suitable sensor, such a photo-sensor attached to the platen, is used. In particular, the movable rod-like element is first abutted against the half side of the book before the platen toward the printing head is stopped when a part of the rod-like element (for example, a lower end therof) is detected by the sensor attached to the platen, whereby an abutting of the platen against the half side of the book can be obtained.
Nevertheless, this detection system cannot function properly when the printing operation carries over from one half side of the opened book to the other half side thereof. In particular, when the printing is carried out on the other or trailing half side of the book, with regard to the direction in which the book is moved during the printing operation, after the printing of the leading half side thereof, the gap adjusted with respect to the leading half side of the book must be re-adjusted with respect to the trailing half side thereof. This re-adjustment, however, cannot be properly carried out by the detection system as mentioned above, because the rod-like element is abutted against the trailing half side of the book at a location close to the center-holding line thereof. Namely, a portion of the trailing half side of the book which is close to the center-holding line thereof does not represent a proper thickness of the trailing half side of the book, because the portion concerned is curved due to the binding of the leaves of the book.